Accuracy

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debenriver
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Location: Maine USA and Suffolk England
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Accuracy

Post by debenriver » Wed Mar 20, 2013 8:48 am

Hi Eric

When I draw full size drawings to send off as DXF files, I draw a 1000 x 100 rectangle on them so that the receiver can check that the drawing has opened at the correct scale (because they don't always).

I have noticed that if I draw a 1000mm line and a 100mm line, then close the file, when I reopen it the 1000mm line is 1000.0015 and the 100mm line is 99.9998mm. Same if I draw a 100mm circle. When I reopen the file it is 100.0002 x 100.0019

The same minor differences occur on scale drawings too.

I know these are tiny tiny amounts and not relevant in practice – but I'm sure earlier version didn't do this. Or am I mistaken??

Best regards

George

Eric Pousse
Posts: 730
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: Accuracy

Post by Eric Pousse » Thu Mar 21, 2013 7:57 pm

Bonjour George,

It is a limitation of the system binaire which is use to store data in computers.
You can't have an unlimited accuracy with numbers.
In RealCADD, you can work an unit from kilometer to millimeter and you can change the unit when the drawing is begun. So I have to choose a system to store the number to be able to use it with the unit to display them from kilometer to millimeter because I want that RealCADD stay a unspecialized drawing software.
Probably that it is possible to have a better accuracy if the unit can't be changed.
All that to say that for me, if you work in millimeter as unit, an accuracy of 2 digits is enough.
Perhaps it would be better that I limit the available accuracy in function of the unit chosen.

Thanks.
Eric Pousse

debenriver
Posts: 513
Joined: Sat Dec 03, 2011 9:19 pm
Location: Maine USA and Suffolk England
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Re: Accuracy

Post by debenriver » Fri Mar 22, 2013 8:21 am

Hi Eric

Thanks for the explanation. Now I think about it, of course it must be like this. So it was a pretty stupid question! Personally I like the arrangement just as it is with the ability to select a range of decimal points in all units. For some reason I work in mm with four places of decimals displayed – which is of course quite ridiculous for a wooden boat where 1mm is the most accurate you can achieve in practice.

It is so easy to get obsessed with accuracy, which I think I am guilty of! But with most everything CNC cut, even wooden parts become very accurate.

Once again, thank you for answering a pretty stupid question

George

Eric Pousse
Posts: 730
Joined: Sat Dec 03, 2011 12:31 pm
Location: Tours - France

Re: Accuracy

Post by Eric Pousse » Mon Mar 25, 2013 8:11 am

No problem, George.
Eric Pousse

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